Technical Field
The present invention relates to a hydromagnetic desalination cell having a rectangular flow conduit, a brine desalination system, and method of desalinating brine water using the desalination cell.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Desalination of sea water is common in the Middle East and the Caribbean, and is growing fast in the USA, North Africa, Spain, Australia and China. It is also used on ships, submarines and islands where freshwater is not readily available. Desalination of ground water is also common in the Middle East, Africa, and Australia. Currently, there are six basic techniques that can be used to separate salt from water; and these include distillation, freeze desalination, reverse osmosis, electrodialysis, ion exchange, and electrostatic deionization. Distillation and freezing involve removing pure water, in the form of water vapor or ice from a salty brine. Reverse osmosis and electrodialysis use membranes to separate dissolved salts and minerals from water, while ion exchange involves an exchange of dissolved mineral ions in the water for other, more desirable dissolved ions as the water passes through chemical “resins.” Commercial desalination techniques in use today include: reverse osmosis, which uses pressure to drive water through a membrane leaving the salt behind; thermal methods, which use heat to distill water while recapturing heat from vapor condensation; and electrodialysis, which uses an electrical potential to drive ions through a membrane leaving the water behind.
Although reverse osmosis is the most widely used technology, it has several disadvantages. For example, the water recovery is only between 30 to 60% and the disposal of the brine water is a major environmental issue. The membranes are expensive and can become clogged by scale and fouling, which requires frequent washing and replacement. Disposal of the membranes is also another environmental issue. Further, reverse osmosis is also very energy demanding.
In electrodialysis, brackish water is pumped at low pressures between flat, parallel, ion-permeable membranes that are assembled in a stack. Membranes that allow cations to pass through them are alternated with anion-permeable membranes. A direct electrical current is established to cross the stack by electrodes positioned at both ends of the stack. This electric current pulls the ions through the membranes and concentrates them between each alternate pair of membranes. Partially desalted water is left between each adjacent set of membrane pairs. Scaling of the membrane to remove accumulated salt is avoided in most electrodialysis units by operationally reversing the direction of the electrical current around the stacks at predetermined intervals.
The use of an electrostatic field produced by two electrically charged surfaces to separate ions has been proposed by MacGregor (U.S. Pat. No. 4,948,514—incorporated herein by reference in its entirety), and has been known since then as capacitive deionization. The main problem with such methods is that positive ions accumulate on the negative surface and negative ions accumulate on the positive surface forming ion layers on the order of a few Angstroms, a phenomenon known as “double layer”. This phenomenon creates a reverse voltage that neutralizes the electric filed inside the pipe, preventing further separation of ions. Several techniques were then proposed to overcome this problem, e.g. using ion selective membranes.
Boucier et al. (U.S. Pat. No. 8,460,532—incorporated herein by reference in its entirety) reported a deionization and desalination method using electrostatic ion pumping. Surface charge is applied externally, and is synchronized with oscillatory fluid movements between substantially parallel charged plates. Ions are held in place during fluid movement in one direction (because they are held in the electrical double layer), and released for transport during fluid movement in the opposite direction by removing the applied electric field. In this way the ions, such as salt, are “ratcheted” across the charged surface from the feed side to the concentrate side.
Another desalination and water purification method was proposed by Hoenig et al. (U.S. Pat. No. 8,016,993—incorporated herein by reference in its entirety). Salt water is bubbled, aerated, or sprayed to cause breaking bubbles along the surface of the salt water. An electric field is applied above the surface of the salt water. Fresh water droplets and vapor, released in the process of bubble rupture, are then pulled away from the surface of the salt water by the electrostatic field and collected for consumption.
A method and apparatus for purifying liquids in electric field was disclosed by Wildermuth, G. W. (U.S. Pat. No. 5,128,043—incorporated herein by reference in its entirety). The method establishes laminar flow of the liquid, passing the liquid through an electric field transverse to the direction of flow to induce mobility of particles away from a negative field surface, separating the liquid into zones.
Edinger, W. J. (U.S. Pat. No. 7,229,555—incorporated herein by reference in its entirety) proposed to use an electrostatic field to prevent biofouling of membranes in reverse osmosis desalination systems. The technique reduces the cost of maintenance of reverse osmosis systems.
A desalination device using selective membranes and magnetic fields was proposed by Penas Ballester et al. (US 20110147295 A1—incorporated herein by reference in its entirety). A device was designed to desalinate brackish water which combined action of magnetic fields generated inside the device and ion-selective membranes, thus obtaining two separate water currents, one with a low salt concentration and the other reject current with a high salt concentration. The device comprises an external cylindrical body of magnetized iron (1), an inner body also cylindrical and made of the same material (2) and an intermediate chamber (3) in which are placed a series of ion-selective membranes (6 and 7) arranged radially around the axle common to all of the bodies, and placed alternately such that each negative-ion selective membrane has a positive-ion selective membrane on either side.
Warren et al. (US 2004/0262234—incorporated herein by reference in its entirety) disclosed an apparatus and method for the purification of fluids using magnetic-field desalination that does not use electrodes. However, it uses a rotating magnetic field and ion-selective-membrane batteries.
A method and apparatus for separating ions from a fluid stream was proposed by G. Richard, G (U.S. Pat. No. 6,783,687—incorporated herein by reference in its entirety). A magnetic field and an electrostatic field are established across a processing zone through which the fluid stream flows so that the flow vector of the fluid stream, the flux lines of the magnetic field, and the vector of the electrostatic field are mutually orthogonal. The resulting high and low ion effluents may be further processed. No thermal input is required. No vacuum, reverse osmosis or reduced pressure distillation is involved.
A device for electromagnetic desalination of sea water was proposed by Imris, P. (EP1880980—incorporated herein by reference in its entirety). The device used a combination of electrically generated high frequency magnetic field and electrostatic capacitive deionization in a specially designed conduit to separate salt ions of sea water from the stream of water to obtain a fresh water stream, while the ions are forced by the alternating magnetic and electric field to go through separate discharging conduits.
During the past 20 years there has been an ever-increasing interest in the treatment of fluids flowing in conduits by means of magnetic devices which are externally attached to the conduits transmitting the fluids. However, precipitates generally cause problems in these systems by adhering to the inner walls of the conduits and, even if the precipitates are non-corrosive, will thereby decrease the effective cross-sectional area of the conduits as well as increasing the flow resistance within the conduits.
Attempts to overcome such issues include work by Weisenbarger, G. M. (U.S. Pat. No. 4,995,425—incorporated herein by reference in its entirety). The proposed magnetic fluid conditioner for abating the adherence of precipitates in conduits can be used with a variety of liquids and/or gases which contain unwanted compounds capable of adhering to the inner walls of the fluid transmitting conduits. The magnetic fluid conditioner has means for directing the outwardly radiating magnetic flux toward the fluid conducting conduits to thereby increase the magnetic flux acting on the liquid and/or gas flowing in the conduits.
A magnetic apparatus for preventing deposit formation in flowing fluids is also described by Florescu, V. et al. (U.S. Pat. No. 5,453,188—incorporated herein by reference in its entirety), in which an apparatus and method for preventing and minimizing the formation of deposits of parrafin, asphaltene, and scale on the inside of downhole oil string line and on the surface of flow transmission lines is reported. Deposit minimization is performed by increasing the turbulence of various electrically-charged microscopic particles populating crude oil colloidal suspension, using effects of the Lorentz force acting upon such flowing fluid. A plurality of spaced-apart permanent magnet disc assemblies are disposed perpendicularly to a fluid flow.
Another method and apparatus for magnetically treating a fluid was described by Harcourt, G. A. (U.S. Pat. No. 5,683,586—incorporated herein by reference in its entirety). The fluid is passed along a pipeline having a permanent magnet aligned therewith, and a coil, rounded at each end, is wrapped around both the pipe and the magnet. Magnetic flux is enhanced by providing a diode in each turn of the coil surrounding the magnet and pipe. Optionally, a collector plate may be provided in the coil remote from the pipe.
Another device for magnetic conditioning of fluids was described by Mercier, D. (U.S. Pat. No. 5,837,143—incorporated herein by reference in its entirety), which describes a process and a device for the magnetic treatment of fluid as the fluid moves in successive magnetic fields, including a sheet having adjacent transverse bands each of the same width. Each band is charged with magnets oriented alternatively NS/SN or NNSS/SSNN perpendicularly to the plane of the sheet so that successive transverse bands adjacent to each other present upper polar faces alternately having polarities S, N, S, N . . . S,N or S,S, N,N, S,S, N,N, . . . S,S, N,N.
A desalination device with a rotatable magnet is reported by Macleod, P. (WO/2014/001741—incorporated herein by reference in its entirety). This device includes a N and S polarity at the ends of a rotational axis creating a torroidal magnetic field, a means to rotate the magnet, and at least two adjacent and stacked water conduit, adjacent the magnet each having a water inlet and water outlet at a center of the conduit and a second water outlet around the first water outlet. In use, salt water can be passed into the conduit water inlet with said magnet rotating and positive and negative ions in the water migrating away from the conduit center whereby water can then be extracted from the first water outlet which is ion free, and the remaining salt water being extracted from a second water outlet.
In view of the forgoing, an objective of the present invention is to provide a hydromagnetic desalination cell having a rectangular flow conduit, a brine desalination system incorporating the hydromagnetic desalination cell, and a method of desalinating brine water using the desalination cell.